c

py-polars/tests/unit/datatypes/test_float.py

@@ -1,6 +1,7 @@
-import polars as pl
 import pytest
-from polars.testing import assert_series_equal, assert_frame_equal
+
+import polars as pl
+from polars.testing import assert_series_equal
 
 
 def test_nan_in_group_by_agg() -> None:
@@ -38,7 +39,7 @@ def test_nan_aggregations() -> None:
 
 @pytest.mark.parametrize(
     ("s", "expect"),
-    (
+    [
         (
             pl.Series(
                 "x",
@@ -67,7 +68,7 @@ def test_nan_aggregations() -> None:
             ),
             pl.Series("x", [0.0, 1.0, float("nan")]),
         ),
-    ),
+    ],
 )
 def test_unique(s: pl.Series, expect: pl.Series) -> None:
     out = s.unique()
@@ -117,6 +118,8 @@ def test_hash() -> None:
 
 def test_group_by() -> None:
     # Test num_groups_proxy
+    # * -0.0 and 0.0 in same groups
+    # * -nan and nan in same groups
     df = (
         pl.Series(
             "x",
@@ -158,6 +161,7 @@ def test_group_by() -> None:
 
 
 def test_joins() -> None:
+    # Test that -0.0 joins with 0.0 and nan joins with nan
     df = (
         pl.Series(
             "x",
@@ -176,6 +180,7 @@ def test_joins() -> None:
     )
 
     for join_on in (
+        # Single and multiple keys
         ("x",),
         (
             "x",
@@ -229,3 +234,25 @@ def test_joins() -> None:
             .to_series()
         )
         assert_series_equal(expect, out)
+
+
+def test_first_last_distinct() -> None:
+    s = pl.Series(
+        "x",
+        [
+            -0.0,
+            0.0,
+            float("-nan"),
+            float("nan"),
+            1.0,
+            None,
+        ],
+    )
+
+    assert_series_equal(
+        pl.Series("x", [True, False, True, False, True, True]), s.is_first_distinct()
+    )
+
+    assert_series_equal(
+        pl.Series("x", [False, True, False, True, True, True]), s.is_last_distinct()
+    )